The invention relates to a divided flywheel with at least two mutually rotatable centrifugal mass elements, which are drive-coupled to each other flexibly by means of a spring arrangement and non-positively by means of a slip clutch arrangement. The spring arrangement has compression springs arranged tangentially to the flywheel axis, which springs are in each case accommodated in windows of at least two mutually rotatable discs connected directly or indirectly to the two centrifugal mass elements.
In the case of such a divided flywheel known from German Published Unexamined Patent Application (DE-OS) 36 10 871, the spring arrangement and the slip clutch arrangement are arranged in series and radially one above the other, the spring arrangement being accommodated radially within the slip clutch arrangement. The flux of force from one to the other centrifugal mass element thus runs successively via the spring arrangement and the slip clutch arrangement or in the reverse direction.
The slip clutch arrangement is of two-stage design, two ring discs being arranged radially one over the other and engaging with each other positively by radial projections and recesses with play in circumferential direction, as its one side connected to the spring arrangement, and a friction surface arrangement arranged on the centrifugal mass element being provided as the other side of the slip clutch arrangement connected to the said centrifugal mass element, which friction surface arrangement interacts non-positively with the ring discs. If, therefore, an adequate torque is transmitted through the spring arrangement firstly the radially inner ring disc connected indirectly to the spring arrangement slips through relative to the friction surface arrangement until the play between the projections and recesses of the two ring discs in circumferential direction is used up. With the same relative direction of movement, now the ring discs can only slip through together with respect to the friction surface arrangement; this of course only happens if a correspondingly increased moment is transmitted via the spring arrangement.
This known divided flywheel is not yet satisfactory with regard to its stability because, in particular, the spring arrangement is highly loaded by the constant relative movements of the centrifugal mass elements. This also applies to such operating phases in which only vibrations of relatively low amplitudes occur in the respective drive train and the relative movements of the centrifugal mass elements have a vibration-similar character.
Therefore, it is an object of the invention to create a divided flywheel which is distinguished to a particular extent by low wear.
This object is achieved according to certain preferred embodiments in that the spring arrangement is arranged within an annular chamber filled with lubricant, which chamber is closed off radially outwards by a wall arrangement, encasing the spring arrangement in a U-shaped manner from radially outside and consisting of parts solidly or integrally interconnected, and radially inwards by a seal arrangement arranged radially within the spring arrangement between mutually rotatable parts.
This arrangement according to the invention ensures a constant lubrication of the spring arrangement and thus an extremely low wear of the same. Since no gaps radially outside the spring arrangement between mutually rotatable parts have to be sealed off, a virtually absolute tightness of the annular chamber is ensured during operation, i.e. with rotating flywheel. Due to the centrifugal forces, the lubricant is namely forced radially outwards against the annular wall arrangement surrounding the spring arrangement in a U-shaped manner. The seal arrangements accommodated radially within the spring arrangement thus essentially only have to prevent an escape of the lubricant when the flywheel is at a standstill.
According to a particularly preferred embodiment of the invention, it is provided that the slip clutch arrangement is also arranged within the annular space filled with lubricant. This achieves a significant increase in the service life of the friction elements.
It is provided in this case in a particularly expedient way that the slip clutch arrangement is of two stage design in the way set out at the beginning and basically known per se. With accommodation within the chamber filled with lubricant, the projections and recesses of the ring discs of the slip clutch arrangement interact in the manner of hydraulic dampers. Each projection of the one ring disc namely divides off within the recess accommodating it or between neighbouring projections of the respective other ring disc seen in axial view of the ring discs two chambers from each other which, depending on the position of the ring discs, have different sizes relative to each other. These chambers are interconnected via a gap, which is formed between the edge of the projection of the one ring disc, facing the respective other ring disc, and the opposite edge of the recess of the other ring disc. Thus, upon movement of the projection of the one ring disc within the recess, hydraulic medium is always displaced on the one side of the projection and fed through the gap to the other side of the projection. This effect is particularly pronounced if the friction surfaces interacting with the ring discs substantially cover or close off the region of the projections and recesses on the front side of the ring discs.
Moreover, the shape of the edge of the recess on the ring disc opposite the projection of the other ring disc may be designed in such a way that the gap width changes upon relative rotation between the ring disc parts. This allows it to be achieved that the higher damping resistance caused by a narrow gap width occurs with certain relative positions of the ring disc parts.
In addition, according to a preferred embodiment of the invention, it is envisaged to arrange as appropriate the friction surface arrangement interacting with the ring discs with at least two friction surface parts arranged radially one above the other corresponding to the ring discs such that in each case one ring disc interacts with only one friction surface part. This gives rise to the possibility of bracing the friction surface parts with different contact pressures against the ring discs, so that the individual stages of the slip clutch arrangement are capable of transmitting different torques.
In particular, there is in this case the possibility of impinging the one friction surface part with a speed-dependent contact pressure in the sense of an increase in the contact pressure upon speed increase.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.